1. Field of the Invention
The present invention relates generally to aqueous-based, urethane-containing, coating compositions having a combination of flame retardant and desirable physical properties, to urethane prepolymers suitable for use in such compositions, to a method of preparing such compositions and to the use of such compositions to impart desirable physical properties to coated substrates. More particularly, the invention relates to aqueous based urethane coating compositions wherein the urethane component comprises the reaction product of (a) a prepolymer of a halogenated diol, a second diol which is either a carboxy group, a sulphonate group or a tertiary amine containing diol, a polyol and an organic diisocyanate and (b) an active hydrogen containing chain extender.
2. Description of the Prior Art
Aqueous-based, urethane-containing, coating compositions have been described in the literature. See, for example, U.S. Pat. Nos. 3,870,684; 4,066,591; 4,108,814 and 4,335,029. However, for a variety of applications, the physical properties, including the fire retardancy, of coatings prepared from these compositions has been less than satisfactory. The use of additives to impart fire-retardant properties to polyurethanes is commonly practiced in the industry. See, for example, U.S. Pat. No. 3,956,233. These additives include phosphorus or halogen containing compounds and antimony oxide. These various external additives are relatively low molecular weight materials which readily migrate from the resin matrix. Especially where used in thin film coating applications, these additives are readily removed during washing or dry cleaning which reduces the fire-retardancy and alters the properties of the coated product.
It is also known that the incorporation of halogens and/or phosphorus into polymeric organic compounds will improve the fire-retardancy of the polymers, and this concept has been followed in the development of fire-retardant paints and coatings. See, for example, U.S. Pat. Nos. 3,681,281 and 3,794,617.
Finally, the use of reactive intermediates to impart fire-retardant properties to polyurethanes is also known in the art. These intermediates are organic phosphorus compounds and halogenated compounds containing active hydrogens which enable them to react with organic isocyanates or isocyanate terminated prepolymers to form polyurethanes. See, in this regard, U.S. Pat. Nos. 3,639,295 and 3,778,408 which disclose organic-solvent based flame-retardant polyurethane coating compositions containing the reaction product of a halogen containing polyol, a phosphorus containing polyol and an organic isocyanate.